Electric switches which operate from one contact condition to another in response to a thermal latch mechanism have been known heretofore. A common device of this category is a circuit breaker used to protect a device or a circuit from damage due to excessive currents. The circuit breaker contacts are manually operable to open and close the circuit, and are latched in the closed position by a thermal element. Excessive current flowing through the circuit breaker cause the thermal element to release the contacts to the open condition, disconnecting power to the protected device or circuit.
Another switch of the aforementioned type is a time delay thermal release switch wherein manual movement to close the switch contacts against a thermal release latch also energizes the thermal circuit. Automatic opening of the switch contacts is dependent upon the time required to heat the thermal latch element sufficiently to release the contacts. An example of this type of switch may be found in U.S. Pat. No. 2,507,949 issued May 16, 1950 to J. K. Asder. This switch further discloses a mechanical adjustment feature to change the time interval. The time delay interval provided by this type of switch is normally of relatively short duration.
My copending application Ser. No. 157,698 filed June 9, 1980 and assigned to the assignee of this application discloses still another type of manually operated thermal release switch. In that application, a manually operable switch includes an electro-thermal latch for holding the switch in the on position. Provisions are made to energize the thermal latch from a remote location to turn the switch off.
While the foregoing switches are all useful for their intended purposes, this invention relates to improvements thereover.